Axial flow combines use one or more longitudinally arranged rotors which are rotated in associated chambers, which chambers are partly constituted by threshing and separating concaves. The crop material is subjected to a much longer threshing and separation cycle than in conventional combines and therefore, the efficiency of axial flow machines is greater. A higher degree of separation is reached and the grain losses are reduced.
The concaves are provided above a cleaning system and constitute the lower portion of the chamber. The top portion of the chamber comprises a curved cover which has, at its inner surface, a set of fins or vanes to guide the crop rearwardly along a spiral path to the end of the threshing and separating zone.
The pitch angle α, of the vanes, has a direct influence on the time interval the crop remains inside the chamber and hence on the chances for the wheat, beans, or grain to be separated from the straw or chaff. A larger pitch angle will increase the rearward speed of the crop flow, reduce the dwelling time, and increase the portion of wheat, beans, or grain which, rather than being separated through the concaves, is instead deposited onto the field, i.e, “rotor losses”. To the contrary, a smaller pitch angle will reduce the rearward speed, increase the dwelling time, and reduce the “rotor losses”.
There are three types of axial flow combine rotor designs, i.e., (1) the Case brand model axial flow combine which has a single rotor; (2) the New Holland brand, model axial-flow combine which has a pair of rotors mounted side-by-side; and (3) there are hybrid combines having a transverse threshing cylinder and a pair of axial separating units.
The hybrid combines are disclosed in, for example, U.S. Pat. Nos. 4,408,618; 4,574,815; 4,611,605; 4,611,606; 4,739,773; 4,875,891; 4,884,994; and 4,969,853. Adjustability of the vanes within the rotor has been an on-going issue in combine designs. Small grains, such as rice, do not have to remain in the separating zone as long as corn, so it is desirable when smaller grains are being threshed to have a steeper angle for the vanes or fins than when threshing, for example, corn. However, it is unduly time-consuming to reposition each vane individually, especially because no crop harvesting can be accomplished during the period of adjustment.
U.S. Pat. No. 4,244,380, issued to Richard A. DePauw, et al., discloses, a Case brand model single rotor machine having a means for selectively and simultaneously adjusting the position of the vanes to change the rate of movement of the crop material through the casing. A three-bolt type of vane is employed which pivots or swivels at the first or center bolt and which locks down at either end using the two remaining end bolts. The two bolts at either end of the vane each move in their respective helically cut slot and slide over to a detent which secures the bolts and the vane in a different position. A small sheet metal cover plate covers each helical slot. One drawback to this design is that since the detents are under the small cover plates, and hidden from view, one cannot immediately determine the degree to which the vane has been adjusted. Also, grain and debris tend to leak out of the slots when the end bolts are tightened down. Furthermore, there are drawbacks to using this design on the New Holland brand machines with twin rotors because there is less space to access the center bolts and the operator has more difficulty making the other adjustments needed. Additional drawbacks include the fact that the cover plate tends to rotate and will not seat properly against the top cover, perhaps owing to the instability of the pivot bolt. Finally, certain structural weaknesses of this design lead to unwarranted stresses and structural deformation for the vanes.
U.S. Pat. No. 5,334,093 attempts to address the problems associated with axial separators that comprise a pair of side-by-side axial separator units each having a rotor. Rather than adjust the vanes, they chose to simply replace the top covers and their respective vanes. Therein each axial separator unit is provided with three detachable covers having inwardly projecting spiral vanes. The first cover is provided with at least five spiral vanes. The first vane has an angle of inclination of 45°, the second, third and fourth vanes have an angle of inclination of 30°, and the fifth vane has an angle of inclination of approximately 25°. Accordingly, in small grains, such as rice, the second and third covers each have at least four vanes all with an angle of inclination of approximately 20°. For corn, the second and third covers each have at least four vanes, all with an angle of inclination of approximately 10°. The second and third covers are designated to be interchangeable depending on the crop. However, this system is undesirably time-consuming.
U.S. Pat. No. 6,447,394 discloses a New Holland brand type rotor design for the twin rotors where the pitch angle of the rotor fins has been optimized with respect to power requirements and rotor losses but are still fixed in design rather than being adjustable.
An axial flow combine side-by-side rotor design with adjustable vanes that would solve the problems of the prior art would be a significant advancement in the art and would satisfy a longfelt need.